This disclosure relates to poly(arylene ether) compositions with a combination of low melt viscosity and high heat deflection temperature.
Poly(arylene ether) resins are an extremely useful class of high performance engineering thermoplastics by reason of their hydrolytic stability, high dimensional stability, toughness, heat resistance and dielectric properties. They also exhibit good mechanical performance and high glass transition temperature values, typically in the range of 150° to 210° C. This unique combination of properties renders poly(arylene ether) based compositions suitable for a broad range of applications. Poly(arylene ether) polymers typically have relatively high molecular weights and possess high melt viscosity with intrinsic viscosity values typically greater than about 0.3 dl/g, as measured in chloroform at 25° C.
It is desirable to improve the melt viscosity capability of poly(arylene ether) compositions. Melt viscosity capability is the ability of a composition to flow freely at elevated temperatures during various processing stages such as extrusion and molding. The melt viscosity can impact the size and type of part that can be prepared with the composition. It has been suggested to improve the melt viscosity of poly(arylene ether) compositions by decreasing the molecular weight of the poly(arylene ether) polymers; however, lower molecular weight sometimes adversely affects other properties such as impact strength. Alternatively, poly(arylene ether) compositions are often prepared with flow promoters or plasticizers such as polystyrene, particularly crystal polystyrene, saturated polyalicyclic resins and terpene phenol to impart high flow to the resulting composition. Polystyrene, terpene phenol and other such flow promoters reduce the heat deflection temperature (HDT) of the product. Additionally, some flame retardants also act as plasticizers and increase the melt viscosity capability.
Efforts to improve the flow characteristics of poly(arylene ether) resins with minimal or no loss of HDT values and impact properties have been made. One approach calls for the addition of a resinous additive comprising vinyl aromatic monomers or a hydrocarbon containing at least 35 weight percent (wt %) aromatic units.
Other approaches have included compositions comprising a blend of two or more poly(arylene ether) resins with one resin having a high intrinsic viscosity values and the other having low intrinsic viscosity. While these approaches have been promising, they have been primarily directed to compositions containing significant amounts of flame retardant and/or plasticizer which has impacts the heat deflection temperature.